1. Field of the Invention
This invention relates to a shaft coupling comprising two coupling members adapted to be associated with respective shafts, one of said coupling members being formed with an even number of bores having a uniform angular spacing, a plurality of pistons, each of which is slidably mounted in one of said bores and has beveled or convex inner end faces, and means for applying fluid pressure to the other end face of each of said pistons, wherein the other coupling member is formed on its surface facing the first-mentioned coupling member with an annular series of elevations and depressions which are engageable by said inner end faces of said pistons.
2. Description of the Prior Art
Various types of shaft couplings are known. Such couplings comprise so-called multiple disc clutches in which the friction between the discs can be increased in that the discs are forced against each other by means of a fluid-operated piston. The torque transmission capacity of such clutches will depend on the slip between adjacent discs and said slip will depend on the contact pressure. If such clutches are frequently engaged and disengaged or a slip between discs occurs for a relatively long time, the discs will be strongly heated and the clutch must be cooled. Such cooling requires an additional expenditure and increases also the wear of the discs. Hydrostatic transmissions are known, which comprise a pump and a motor and in said pump and in said motor comprise pistons, which are interconnected by a hydraulic linkage and cooperate with respective swash plates. The torque transmission capacity of such transmissions can be controlled by an adjustment of the inclination of the swash plate. Such transmissions have a highly complicated, bulky structure. Besides, liquid friction couplings are known, which comprise a housing, which is filled with a viscous liquid and constitutes one coupling member, whereas the second coupling member comprises a shaft, which extends into and out of the housing. First and second sets of discs are non-rotatably connected to the housing and the shaft, respectively, and the discs of said sets interdigitate. Different from the conventional multiple disc couplings the transmission of torque in liquid friction couplings is not due to the frictional contact between the discs but is due to shearing forces taken up by the viscous liquid and the torque transmission capacity will depend on the speed difference between the two coupling members. An arbitrary control of the torque transmission capacity is difficult. In particular, the torque transmission capacity cannot be decreased to zero by a control. Another disadvantage is the high dependence on the temperature-dependent viscosity of the liquid.